Best Free CAPTCHA Software of 2024

MTCaptcha is a privacy-focused and accessible captcha service. It offers an adaptive invisible noCaptcha that ensures easy verification for humans while posing a challenge for bots. MTCaptcha complies with GDPR and WCAG, guaranteeing the protection of your data without any sharing or selling to third parties. The captcha images are colorblind-safe, and the widget is fully VPAT compliant, optimized for screen readers. Supporting multiple languages, MTCaptcha can be fully customized to match any webpage. It also provides audio support, enhancing accessibility for visually impaired users. Trusted by Enterprises, Government, NGOs worldwide, MTCaptcha is available in major languages and functions globally, including in China. Its adaptive Risk Engine effectively detects and responds to threats, maintaining the balance between challenging bots and facilitating human verification.

ALTCHA is a CAPTCHA alternative which uses a proof of work mechanism to protect websites and online services against spam. ALTCHA uses a mechanism of proof-of-work to protect your website, online services, and APIs from spam and unwanted material. Unlike other solutions ALTCHA is open-source, self-hosted and free. It does not require external services and does not use fingerprinting or cookies.

Friendly Captcha is used by organizations of all sizes, from startups to large corporations, to protect their online services and websites against spam and abuse. Friendly Captcha protects your users' privacy and works automatically so they don't need to do anything. Friendly Captcha is a new way to protect your website and online services against spam and bots. It uses the underlying mechanisms in the blockchain. Friendly Captcha doesn't rely on tracking users or exploitation of personal data. Plus, your users will no longer be burdened with tedious labeling tasks. They don't need to do anything.

Turnstile provides website visitors with a CAPTCHA-free experience, without any frustration. All it takes is a small piece of free code. Turnstile also stops abuse and confirms that visitors are real, without the data privacy concerns of CAPTCHAs or the awful UX they force on users. Give your website visitors an even more enjoyable experience. Turnstiles are 100% transparent to visitors, as there is no visual puzzle to confirm their authenticity. Turnstile protects the privacy of your web visitors without compromising effectiveness. We never collect data for retargeting ads, unlike other CAPTCHA solutions. You can deploy in just minutes using a small code snippet. Humans waste time and create frustration by spending 500 years a day on CAPTCHAs. Cloudflare has built a better CAPTCHA alternative with Managed Challenge, and now Turnstile.

CaptchaFox is used by online businesses to protect and safeguard their websites and services from automated bot attacks. CaptchaFox provides protection against account takeovers, credential stuffings, spam, and scalping, while also complying with global privacy legislation, such as GDPR and CCPA. Privacy is protected by minimizing data collection and retention when verifying your users. CaptchaFox uses a variety data signals and dynamic responses challenges to verify the genuineness of visitors, without the use or tracking cookies. The challenges are low friction for humans and difficult for bots. The service is available across multiple languages, and can scale to the incoming traffic via our global infrastructure. Enterprise customers have access to advanced threat insights for complete risk awareness.

Prosopo Procaptcha redefines the user verification process with a unique, decentralized approach that emphasizes privacy and security. It's an innovative solution that offers an alternative to centralized CAPTCHAs, which often compromise privacy. By choosing Prosopo Procaptcha you not only protect your applications from malicious actors and bots, but also maintain the privacy of your users.

BotDetect™, CAPTCHA generator is an automated form-security solution that prevents automated form posting. It uses a combination of measures that are simple for humans and difficult for bots. BotDetect provides an audio Captcha alternative that allows websites to be accessible to people with impaired vision. This will allow you to create Section 508 and WCAG compliant websites. Our former competitors are now only two viable ones after years of Google's inexplicable abuses of their paid and organic search monopolies. BotDetect was the only Captcha generator that offered a variety of Captcha sound and image algos during its first decade. Each of them was easy to understand, but the random use multiple Captcha generation algorithms made it extremely difficult to pass the generated captchas automatically.

The TextCaptcha Service provides access to textual CAPTCHA problems via a simple JSON API or XML over HTTP. The question is a textual challenge to be presented to the user. The answers are MD5 hashes for correct lowercased answers. You should be able check responses from real users that you challenge with a question against these checksums. Text CAPTCHAs are more accessible to visually impaired people than image-based CAPTCHAs like ReCAPTCHA. Text is also more flexible, for example if you need to present a challenge via a text-only channel such as SMS or IRC. The problem with text CAPTCHAs, is that they give inherently more information than an image distorted. They can be parsed, and under the right circumstances they are solvable. These simple logic puzzles are now easier to solve using Wolfram Alpha and other contextual parsing tools.